Fix broken input tests

InputPublisherAndConsumer_test currently segfaults due to
null pointer dereference. This is because 0 is passed instead
of a valid pointer to an allocated int32_t. Also, enforce strict
compiler warnings, include signed comparisons.

Bug: 62033391
Test: m -j libinput_tests_InputEvent_test
libinput_tests_InputChannel_test
libinput_tests_InputPublisherAndConsumer_test
libinput_tests_InputTransport_test libinput_tests_VelocityTracker_test
&& adb push out/target/product/taimen/data/nativetest/libinput_tests/
/data/nativetest/
then run the above tests individually, for example
/data/nativetest/libinput_tests # ./InputPublisherAndConsumer_test
and others in a similar manner

Change-Id: Ia030cdbfa22d2bf7bdf6274a337b059ca3f9a6c3